WASHINGTON — U.S. doctors earn more than their European, Canadian and Australian counterparts, with American orthopedic surgeons outpacing their peers by a wider margin than primary-care doctors, a study found.

Primary-care doctors in the U.S. made an average of $187,000 in 2008, according to the study in the journal Health Affairs. Orthopedic surgeons made $442,000. That rate was more than double what the surgeons in Australia, Canada, France and Germany made. British orthopedists made on average about 73 percent as much as their U.S. counterparts.

The disparities are partly due to the inability of private insurers and U.S. health programs’ to extract concessions from orthopedists, wrote co-authors Miriam Laugesen and Sherry Glied. The five other countries studied all have variations on state- run health systems.

“Public-sector fees for hip replacement surgery in other countries are about half as high, on average, as Medicare fees in the United States,” the authors wrote. Private insurance fees account for much of the difference for primary-care doctors, they said.

For example, Medicare, the U.S. health plan for the elderly and disabled, paid an average of about $60 for a primary care office visit in 2008, second to Britain at $66, and double the fee for France’s public health-care system.

Private health plans in the U.S. pay the most of any country studied. A U.S. doctor received an average of $133 for an office visit from private insurers, compared with $129 in Britain, and almost four times as much as doctors in France, according to the study from Laugesen, a health policy professor at Columbia University in New York, and Glied, the assistant secretary for planning and evaluation at the Department of Health and Human Services.

Americans with the highest education levels tend to make more than their peers in other countries across all industries. As a result, doctors demand more to keep up with high-earners in different industries,

The physician incomes were calculated by subtracting doctors’ practice expenses from their treatment revenue, which were tallied from Medicare and public program data, as well as private insurer rates through HealthGrades.com, a third-party data provider, the authors said in the study.

Doctors outside the U.S. earn less while treating a larger share of their countries’ populations, the authors wrote. In Australia, primary-care physicians made an average of $93,000, the lowest of the six countries studied, while orthopedic surgeons made $188,000, second from the bottom. French orthopedic surgeons were the lowest paid in that specialty, at $154,000 per year on average, while primary-care doctors there made $96,000, the second-lowest figure.

The cost of a medical education in the U.S., which isn’t financed by the government to the extent it is in other countries, doesn’t explain the disparities, the authors wrote.

U.S. primary-care doctors made about $5,700 more than the annual cost of their training spread out over their lifetime. Orthopedic surgeons made five times what they had to pay for their training, according to the study.

“Although the tuition cost of medical education in the United States borne by individuals is substantial, it cannot fully account for the observed differences between the earnings of US physicians and physicians in all other countries,” the authors wrote.